I'm aware of the ECL rules for younger dragons in D&D 3.5. I'd like to move away from that system with this, if possible (it is retained as last resort though). Not that it's incompatible here, mind you. More of a hope to broaden my experience.
I want to run a PbP or PbEM with some friends who have a passive interest in RPGs but an active interest in dragons. While most of them are new players, I'm an old DM who is accustomed to teaching newbies much of the time. As such, a complicated rules set isn't a disqualifier.
EDIT: I'm searching for a system where players have dragon companions, such as the Weyrs of Pern series or the movie How to Train Your Dragon.